Effects of canopy gaps on the growth of tree seedlings from subtropical broad-leaved evergreen forests of southern China

Seedling performance, morphology, and leaf characteristics of evergreen tree species from different successional stages of Chinese broadleaved evergreen forests were studied in four simulated gap environments: in 100, 55, 33, and 18% of full sunlight. The first two represent the light regimes of clearings (gaps secondarily become more open due to human activity and natural erosion). The hypothesis was tested that early-successional species achieve their greatest seedling size in clearings and contrast in this respect with late-successional species. Late-successional species were expected to show a stronger morphological response (leaf/root ratio) to clearings than early-successional ones. The results provided some evidence in support of these hypotheses with one exception, namely that late-successional Castanopsis fargesii appeared to be a highly sun-tolerant species. It is suggested that Castanopsis seedlings are competitive in large gaps and clearings.